Airflow control apparatus for cabin pressurizing and engine supercharging



2,471,292 APPARATUS FOR CABIN PRESSURIZING AND ENGINE SUPERCHARGING May 24, 1949. D. G. TAYLOR AIRFLOW CONTROL Filed Dec. 26, 1944 2 Sheets-Sheet l May 24, 1949. D, C.;l TAYLOR 2,471,292

AIRFLOW CONTROL APPARATUS FOR CABINPRESSURIZING AND ENGINE SUPEROHARGING Filed Dec. 26, 1944 2 Shee'tS-Sheet 2 lll.

Patented May 24, 1949 AIRFLOW CONTROL APPARATUS FOR CABIN PRESSURIZ'IN'G AND ENGINE SUPER- 'CHARGING Daniel G. Taylor, `Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware lApplication @December 26, 1944, Serial No. 569,759

UNITED 'STATES PATENT OFFICE .cabin pressure ycan be effectively .controlled -by suitable outlet valve means so long as the super-- ,charger discharge ,pressure .is above the pressure desired in the cabin. Depending on `the Value vof Ithe cabin pressure, the supercharger .discharge pressure is ordinarily above .the cabin pressure. However, under some conditions, such as `cruising when lightly loaded, descending, or the like, the discharge .pressure tends to ifall lbelow that necessary to maintain the 4cabin pressure. Under these conditions, `air flow into the cabin Vdiminishes or stops, thus ,preventing adequate Vvcabin ventilation and .the maintaining of the .cabin pressure.

To prevent .the -supercharger discharge pressure from .falling below that desired, it has been proposed to .provide suitable control apparatus other object Vof this invention; namely, the provision of apparatus to lautornai'lically maintain be above mentioned low liniit of discharge Apressure. With automatic operation, 'the need for throttling an engine is reduced `to a minimum, less manual attention is required by the apparatus, and engine efficiency is Amaintained as high as possible under the circumstances.

The present highly developed electronic supercbarger control apparatus permits a vsingle knob -to control the supercharger discharge .pressurerof 4a plurality of engines simultaneously. However,

air is yusually diverted .from vthe `inbmard .engines only of a multi-:engine aircraft, .hence it -is desii-able, and it has been proposed to provide -control apparatus which znodiiies fthe aotionoi' only the inooard Aengine superchargers in response `to cabin air demands, thus permitting the outboard engines to operate at `maximum -eliiclency at all times.

Ilietause the compensation which is introduced into vthe -turbo-supercharger control system requires a time interval iior "removing same, there may vsituations in which the engines might be endangered by excessive induction pressure. Vror instance, -in descending for a landing Vwith the inboardengines throttled and the turbo-supercharger control system for the inboard 'englues modified to maintain cabin pressure, an might arise `requiring full engine To get `full power, the throttles will be opened and the turbosupercharger boost control will be adjusted for the desired power setting.

However, due to the compemation introduced into the system, thefinboard engine superchargers .may overspeed and Amay provide excessive induc- .tion pressure for a short period of time and cause damage to said engines, this being due to delay in removing the compensation from the control apparatus.

-t is therefore a principal object of this invention to prevent damage to .the inboard supercharger and engines by providing apparatus for .suitabiy compensating the turbo-supercharger control means but oi such nature that the coinvpensaticn is automatically and simultaneously reduced as the turbo boost selector is adjusted for higher power settings. Thus it becomes iinpossible for the compensating means to endanger theengines under any circumstances. It follows that the amount of compensation may be automatically and simultaneously increased as the turbo boost selector is adjusted for lower Vpower setting, thus tending to maintain air flow Ato the :cabin et a desired value.

It is an additional object to Vprovide apparatus of the above nature for modifying the lcontrol means of a turbo-supercharger wherein .the -rate of modification may be manually adjusted.

It is also an object to provide apparatus of theaoove Anature iormodifying the control means of a turbo-supercharger wherein the amount of permissible inodication may be manually adjusted.

it is a further object to provide an inherently safe cabin boost control apparatus for compensating a turbo-supercharger control system.

These and other objects will become apparent upon a study of the following specification and related drawings.

In the drawing,

Figure 1 is a schematic view of the present control apparatus as applied to a four-engined aircraft,

Figure 2 is a more specific schematic showing of the present control apparatus as applied to the No. 3 engine.

In Figure l, pressurized cabin I is schematically shown in its normal position relative to the engines of a four-motored airplane. Engines I and 4 are outboard engines and engines 2 and 3 are termed inboard engines. As will be noted, cabin II) is supplied air from the induction systems of engines 2 and 3. Obviously, cabin boost control I I and turbo boost selector I2 are normally within cabin I0 and arranged to be operated by either the pilot or ilight engineer, the present schematic arrangement being chosen for convenience only.

In the present description, it will be noted that apparatus common to a plurality of engines is numbered by numerals from Ill to 99; apparatus specific to engine No. I by numerals IBB to I99; apparatus specific to engine No. 2 by the same numerals as engine No. I increased by 100; and apparatus speciiic to engines 3 and 4 is numbered similarly to engine No. I but with additions of 200 and 300, respectively. As the basic turbosupercharger control apparatus is similar for each of the engines, the following brief description of the apparatus of engine No. 3 will sufce for all, keeping in mind the above systems of numbering.

Engine No. 3 is furnished air by supercharger 3I-through conduit 3II and a carburetor. The carburetor includes a suitable throttle lever, used in a manner to be described. Supercharger 3I0 is driven by an exhaust gas operated turbine 3M, the exhaust gases being supplied through conduit SI5. It is noted that conduit 3I5 also includes an outlet portion communicating with the atmosphere, said outlet portion being controlled by waste gate SIB operated by lever 3H. When waste gate tie is wide open, exhaust gases pass freely through conduit 3I5 to the atmosphere and no power is developed by turbine 3I4. However, as the waste gate is closed, the

exhaust gases are forced to flow through said i turbine and cause rotation of same at high speed. Turbine 3M is connected in driving relation to supercharger SIU, hence closing waste gate 3I6 is seen to operate 3|!) and provide air under increased pressure for the engine. Waste gate 3I6 is thus seen to be the eiIective control means for the supercharger discharge pressure, and the present control apparatus is used to properly position said waste gate. Although this is the preferred manner of controlling discharge pressure, it is not the only one that can be used, throttling the inlet to the supercharger also being feasible, for instance.

Waste gate 3I6 is adjusted by motor 3I8 operating waste gate lever 3I'I by lever 3I3 and link 320. Motor 3I8 is of the two-phase reversible type wherein the operation of same and direction of rotation depend on the phase relation of the ycurrents supplied the windings of said motor.

One of the motor windings is supplied from the line by the circuit: line wire I3, wire 32I, condenser 322, wire 323, motor 3|8, wire 324, and line Wire I4. The other winding of the motor 3I8 is supplied current from amplifier 325 by wires 326 and 321. As is characteristic of two phase motors, motor 3I8 will not operate when the phase of the current supplied from amplier 325 is the same as that supplied from the line wires, nor, of course, will it operate when current is furnished only one Winding or when no current is furnished. However, if the current supplied through wires 323 and 32I leads that supplied through wires 323 and 323, rotation will take place in one direction, whereas if the current from amplifier 325 lags that supplied from wires 323 and 323, rotation will occur in the opposite direction. Obviously, motor 3I3 operates lever 3I9 through a gear train, not separately shown.

Amplier 325 may be of any suitable type which will maintain the same phase relation in its output current as is possessed by its input signal. Such amplifiers are well known in the art; as an example of this type of amplier, reference is made to the copending application of Albert P. Upton, Serial No. 437,561, led April 3, 1942, Patent No. 2,423,534, issued July 8, 1947; or to the Chambers Patent 2,154,375. Current for operation of amplifier 325 is supplied by the circuit: line wire i3, wire 323, amplifier 325, wire 329, and line wire I3. The signal input source for amplifier 325 comprises wire 333 and grounded wire 253i, wire 333 leading from control apparatus collectively identified by the numeral 332.

Control apparatus 332, as shown in Fig. l, responds to the speed of rotation of turbine 3I4, transmitted through shaft 333, and to induction pressure in conduit SII by connection through tubes 334 and 334. Control apparatus 332, in conjunction with cabin boost control I I and turbo boost selector I2, determines the phase of the signal supplied amplifier 325, as will be more fully explained as the description proceeds.

In addition to supplying air for engine No. supercharger SIG also supplies air for cabin III. Conduit 335 diverts air from conduit 3II into cabin I. Conduit 335 includes a flow sensing and limiting venturi 335. Air pressure upstream of venturi 333 is communicated to cabin boost control II by tube 337, while the downstream pressure, or the cabin pressure, is communicated to control Il by tube I5. Tube I5 may be connected in the throat of venturi 333 but more stable action is obtained by the connections shown. Here, too, it is apparent that other sorts of flow sensing and limiting means may be used, the present apparatus being illustrative only.

The nature of control apparatus 332, as well as cabin boost control I I and turbo boost selector I2, is more fully shown in Figure 2.

Apparatus 332 comprises two electrical networks SI2 and 3I3 connected in series, both of the networks being energized by a plural secondary transformer 341i. Transformer 343 includes primary winding 35| and secondary windings 3152 and 333. The primary winding is energized from line wires I3 and I I by wires 372 and 373, respectively. A follow-up potentiometer comprising wiper 335y and resistor 335 is connected to secondary winding 342 by the circuit: intermediate tap 346 of winding 332, wire 341, resistor 345, Wire 338, and the right-hand terminal of winding 332. Wiper 334 is connected to wire 333 and is moved by arm 331i. Arm 335 is shown connected to arm SIS by link 353 so that Wiper 344 assumes a position dependent on that of waste gate 3I5. Wiper 334 is at the left side of resistor 335 when waste gate SI5 is open. In practice, this follow-up potentiometer is included in the same casing as motor 3I8 and is op- .5 ratedby its output shaft, the present arrangemen't'being` made only for convenience.

A potentiometer including wiper 35| and resistor 352 is also connected to winding 342, the circuit being: the left-hand terminal of winding 342, wire 354, resistor 352, Wire 355, and intermediate tap 355 of said winding. Wiper 35| is actuated by an overspeed responsive device 358, said device being driven from the turbine 3I4 by shaft 333 and its extension 333'. When the turbine assumes an overspeed condition, wiper 35| is moved to the left. Network 3|2 is seen to comprise wiper 345, resistor 345, transformer secondary 342, resistor 352 and wiper 35|.

Associated with overspeed responsive device 358 is acceleration responsive device 359, this latter device also being driven by shaft 333. Device 359 positions wiper 360 in response to the acceleration of turbine 3|il and it, in combination with overspeed responsive device 358, comprises the protective means for turbine 3M. Any suitable speed and acceleration responsive devices may be used, one suitable type being that disclosed in Sparrow application, Serial No. 473,797, filed February 22, 194.3. Wiper is connected in series with wiper 35i by wire 35|.

Wiper 36! is moved to the right across resistor 352 in response to acceleration of turbine 3M, the: initial movements of same having no effect because of a low resistance slide portion or dead spo 362 at the left hand end of said resistor. rIhe left end of resistor 352 is connected to wire 363 and the right end of same is connected to wire 364, and a second resistor 355 is connected in parallel with resistor 352 from wire 353 to 364. Wires353 and are connected to the terminals of transformer secondary winding by wires 366 and 351, respectively. Resistor 355 is swept over by wiper It will be noted that resistor 562, wire 354, resistor 355 and wire 353 formV aA bridge type network 3|3 with wires 35S and 351 as the input current supply means and wipers 35@ and 358 forming the output terminals. Wiper 358 is moved across resistor 355 in response to variations in induction pressure by expansible bellows 369, said bellows being connected to the discharge of supercharger 3|@ by tube 334' and its extension 334', movement being to the left with increase in said pressure. Opposing bellows 359 is an evacuated spring operated bellows 310, bellows 315 being used to neutralize the effect or varying ambient pressure on bellows369. Wiper 338 is connected to terminal 31| of turbo boost control I2 by wire 3'52.

Turbo boost selector I2 comprises a main potentiometer 2G having a resistor 2| and wiper 22. Wiper 22 is adjusted by manually operated knob 23 and is connected through terminal 56 to ground 51. Resistor 2| is connected. to terminals 24 and 25 of secondary winding 25 of a transformer 21 by wires 28 and 29, respectively. Terminal 25 is also connected by wire 35 to terminal 33v of control I2. Primary winding 34 or transformer 21 isconnected to terminals 35 and 35 of control I2 by wires 31 and 38, respectively. A primary winding 4|! of transformer 4| is connected in parallel with primary winding 34 of transformer 21 by wires 42 and 43. Transformer 4I includes a plurality of secondaries |13, 213, 313, and 413 across terminals or" which are connected in parallel resistors |14, 214, 314, and 414, respectively. Wipers |15, 215, 315, and 415 coact with resistorsV |14, 214, 314, and 414, respectively, to form Calibrating potentiometers for' the individual turbo control circuits.- Wipers |15, 215, 315, and 415 are connected to terminals l1|,21l,31|, and 41| by wires |15, 215, 316, andl 515, respectively. The right hand terminals of resistors |14 and 4l4 are connected to wire 30 by wires Ill' and 411i, respectively, and the right hand terminals of resistors 214 and 314 are connested to terminals 213 and 313 by wires 211 and lill, respectively. The present arrangement of the Calibrating potentionieters is but one of several that may be used, as will be apparent to those skilled in the art. rlhe numerals below and along resistor 2i are for convenience in adjusting wiper 22.

Current inputerminals 35 and 36 of control l2 are connected to line wires I4 and i3 by Wires 55 and 4s, respectively.

While turbo boost selector I2 permits simultaneous adjustment of the supercharger discharge pressure or" all four engines, cabin boost tr il may modify the control of the inc .d engine superchargers in' a manner to be escribed. Cabin boost control II is, in this decription, arranged to modify the control of two uperchargers hence it comprises two identical ets oi apparatus. As the turbo control apparatus has been described for the turbo-superof engine No. 3, only the apparatrs of control ll pertinent to engine No. 3 will be described, it being kept in mind that the apparatus rer engine No. 2 is similar in structure and function. While control Il shows separate adjustment means for each of the inboard engines, it is noted that the pairs of control adjustments may be combined if desired.

Cabin boost control ll includes means responsive to the differential of pressure existing between ytubes and said means comprising bellows and connected to tubes l5 and respectively. Switch arm 353, biased to the nt by adjustable spring means is operated the resultant oi the forces exerted by bellows Sti and 552, the arm moving to the right when differential pressure is low and moving to e left when said diiierential pressure is high. ch arm 353 operates between contacts 305 c55 to control the operation of motor 351. Contacts and are rather widely spaced so that an electrical dead spot exists between thus permitting some fluctuation of preswithout causing motor 351 to operate.

Motor is of a reversible two-phase type and operates through gear train 358 to position potentiometer wiper Motor 351 includes a pair of field windings and 335 and the operation and direction oi rotation of said moto-r depends on the phase relation of the currents supplied said windings. Also associated with motor Sill for control or" same is a manually operated switch 35i j'rir of limit switches and a iight A xed resistor 335 is connected eries with winding 359 and a similar resistor is connected in .series with winding 385. If he windings and 385 be energized through r respective resistors, no rotation will take Jce because the current supplied each winding is the same phase. However, ii one of the resistors be shunted out, then the current supplied the winding in se les with said shunted resistor 1.". l that supplied the other winding, and the motor will operate in one direction. lf said resistor be returned to its series connect-ion and the other resistor shunted out, the motor will operate in the opposite direction. The operation of this motor will become more clear when its energizing circuits arey traced in the operating if schedule following the present description. It is noted that the boost control il is energized from 26 volt line wire 5@ to terminal 5l and line wire I4 and wire 53 to terminal 54.

Motor positioned wiper 369 moves across resistor 381 and introduces more or less compensating signals to the turbo control apparatus depending on the position of said wiper, the position of wiper 22, and the position oi manually adjusted wiper 338. The left end of resistor Sti is connected to wire 52 by wire tte and the right end of same is connected by wire 39H to wire t3. Wire 63 connects through terminal 5ft, wire 55, terminal t5, wire t?, and terminal 55 to ground 51, while wire @2 connects through terminal and wire Sii to turbo boost control terminal 33. Manually adjustable wiper 388 coacts with resistoi` 392, the right end of which is connected to wire 62 and the leit end of which is connected to wiper 399 by wire 393. Wiper is connected by wire 394, terminal 39%, and wire 3% to turbo boost control terminal 378.

It is noted that the present turbo-supercharger control system is similar to that disclosed in the copending application of Hubert T. Sparrow et al.,

Serial No. 485,992, led May 14, 1943, now Patent No. 2,466,282, issued April 5, 1949, and reference is made to said patent for a more complete description of said system.

Further, as 'previously made clear, the apparatus for control of the supercharger of engine No. 2 is similar to that described While the present system has been described in relation to a multi-engined aircraft, it may also be used in a single engined aircraft if it be I! desired to provide an adjustable low limit of supercharger discharge pressure for cabin ventilation, pressurizing, or the like.

To more fully explain the present invention,

the following operation schedule describes the operation of the present apparatus under` operating conditions.

Operation In considering the operation of the present control apparatus, it will be noted that the various elements of the apparatus are in their positions of rest, with the airplane stationary and at sea level. Wiper 22 of turbo boost selector l2 is adjusted for zero boost, the induction pressure r sponsive device shows its wiper 363 at a position indicative of atmospheric pressure, the acceleration responsive means 35e has its wiper Bt in a position indicating no acceleration, the overspeed responsive device 353 indicates no overspeed, waste gate 355 is wide open, and wiper Stil. of the follow-up potentiometer is at its extreme left of travel. Further, the switch for the cabin boost control 33! is in its oir position and wiper 3559 is in a position to add no compensating eiect to the turbo boost control system.

As before noted, operation of the waste gate motor Si@ depends upon whether or not amplifier 325 is furnishing a signal voltage to the same. Further, the direction of operation of said motor depends upon the phase relation of th-e current supplied the motor by the amplifier as compared to that of the line current. Since the phase relation of the output of the amplifier depends upon that of the input, an analysis of the control networks will determine whether or not a signal is being supplied said amplifier and the phase relation of same. To expedite a consideration of these networks, the instantaneous current relation existing in the networks during a half cycle may be considered. Then, the left end of each of the networks may be considered negative in potential and the right end positive. Considering the operation oi a network on a half cycle basis, it may be determined whether or not there is a signal resulting from same and the signal will then appear to be either positive or negative in potential. However, with alternating current, a signal which is negative in potential in one instant becomes, a half cycle later, positive in potential. lt is thus obvious that what appears to be positive and negative signals actually represents signals 3.86" different in phase. Therefore, while it is noted that signals of one phase relation will cause the waste gate motor to operate in one direction, and signals of another phase relation will cause said motor to operate in the opposite direction, in this analysis, signals having a positive potential will cause the waste gate motor to operate toward open position and signals having a negative potential will cause said waste gate to be closed.

lit/"ith a 3o volt ting across resistor 2l, wire Si@ is 30 volts positive relative to wiper 22. Assuming that the wipers of each of the Calibrating potentiometers is at a potential 2 volts less than that at the right extreme of their respective resistors, then wiper M5, wire ii'i, and terminal lill, for instance, would be at a potential of 28 volts positive above wiper 22. Following wire 35 through terminal 33, wire til, terminal 5i, wire wiper Bilt, wire 393, wiper wire EBSQ, terminal wire 39%, terminal wire Eil', resistor 3M, wiper dit, wire 376, and terminal Sii, it is seen that the potential at terminal Sii will also be 2S volts positive relative to wiper 22 ior the direct connection through cabin boost control il made no change in the control signal. It is thus noted that with the .adjustments of cabin boost control i i in the positions shown, with wiper Bti? at the extreme left of resistor 389, and wiper 3232 at the extreme left of resistor 392, the cabin boost control is, for all practical effects, nonexistent, and the turbo boost control apparatus may be considered in its normal operation. It should be noted 'that this normal operation of the present turbo boost control is representative of the control apparatuses relating to each of the other engines.

it has now been determined that the voltage signal from the turbo boost control I2 is 28 volts positive. Assuming a 30 volt potential existing across resistors S and 3%, it appears that wiper Sii@ is about l0 volts negative relative to wiper 36B; therefore the output of network SiS is 10 volts negative. Considering that tap 3d@ is about six volts positive relative to tap then from the position shown, wiper Si@ is about six volts positive relative to wiper 35! hence the output of network Si is six volts positive. Adding these voltage signals, because the networks are connected in series, it appears that amplifier 325 is provided at its input terminals with a signal of about 24 volts positive. lt was previously pointed out that positive signals tend to open the waste gate, therefore, the waste gate remains wide open, further operation beyond wide open position of motor dit being prevented by internal limit switches (not shown) Assume now that the aircraft is being prepared for the take-oir". As the power output of the engines is increased preparatory to the beginning of the ilight, it is obvious that the added rate of airiiow through the induction system will cause ,the induction pressure to drop. As will be noted,

as wiper k368 moves to the right, wiper 360 .becomes more negative relative thereto; however, as the total travel of wiper 363 to the right from its previous position permits a change of only about ,20 volts, this in itself cannot cause operation of the waste gate motor. For the take-off of the aircraft, a high power output is ordinarily required from the engines, so let it now be assumed that wiper 22 is moved across resistor 2l to the right to position 8 so that wire 3!) is only 6 Volts more positive than said wiper. Then, assuming that the parts of the cabin boost control remain in their previous position, the potential at terminal 31|, wire 312 and wiper 358 is only 4 volts positive relative to wiper 22. Now, if wiper 358 Aof the induction pressure responsive `controller has moved to a mid-position on resistor 365, and there has been no excessive acceleration, wiper 360 is now 15 volts negative relative to wiper 305i and the output of network 3l3 is 15 volts negative. Further, assuming that Wipers 35i and ili are in their previous positions, then .wiper 3.44 is about S volts positive relative to wiper 35i. Hence the output oi network 312 remains 6 volts positive. Adding these voltage signals, it is noted that there is now a negative signal of about volts impressed on amplier 325. The negative signal causes operation of motor BIS to close the waste gate and to adjust the follow-up potentiometer so that wiper 544 moves to the right across resistor 345. With the conditions as previously stated, motor 350 would continue to close waste gate and wiper 3M would be moved across resistor i545 until said wiper 344 becomes about ll volts positive relative to wiper .'"i

355. At this point, the positive signals and the negative signals of the networks would -be in balance and there would be no resulting signal to the amplifier. However, as the waste gate moves toward closed position, the induction pressure rises and wiper is moved toward the left. This dim Aes the negative signal and therefore decreases the amount of movement required by wiper 5M to the right to balance the system.

Up to this point, it has been assumed there was no excessive acceleration nor was there anis7 overspeed. Obviously, closing movement of the waste gate increases speed of the turbine and, assuming that the rate of increase may be unduly rapid, wiper is moved to the right across resistor 332. Because of the dead spot in the left portion of resistor the initial movement of wiper has no change in the signal condition, but 'further movement to the right tends to make wiper 5350 less negative with respect to 353 and thus to remove the negative signal which causes waste gate closing. Should wiper Seil move to the right of wiper 35B then it would become positive relative to said wiper Seil and would further tend to cause opening of the waste gate. Likewise, movement of wiper to the left due to overspeed tends to make wiper 34e more positive relative to said wiper 35i and thus cause opening of the waste gate. Opening of the Waste gate permits more of the exhaust gases to by- .pass the turbine and thus causes the turbine to decelerate.

As before stated, the above description of operation of the turbo boost control system is that which normally applies to each of the superchargers oi the aircraft, ignoring the cabin boost control. Thus, when the switches of the cabin `boost control are turned to oi the turbo superchargers of each of the engines of the aircraft may be simultaneously controlled by the turbo 11,0 boost selector in the manner described. For a more detailed description of Yoperation of this turbo boost control system, reference is again made to the aforesaid patent of Hubert T. Sparrow et al.

With the turbo boost control system working as previously related, attention may now be directed to the cabin boost control. The pressure to -be maintained in the cabin, as before mentioned, is normally controlled by pressure regulating means, not shown, which .control the iow of air from the cabin. Assume that a cabin pressure of 22 inches of mercury is to be maintained, this prf-usure corresponding to an altitude of about 3,000 feet. Control means 3M may be adjusted to a position of relatively low flow so that, for example, switch arm 303 will engage contact when the diierential of pressure Abetween tubes i5 and 331 is less than 1 in. of mercury and, when the differential pressure rises to 2 in. of mercury or more, arm 303 will engage contact With turbo boost selector I2 adjusted to give only a e volt positive signal, it is noted that the turbo-superchargers are operating to provide a relatively high induction pressure This pressure may be considered `to be Well above the 2,2 oi mercury cabin pressure being maintained, so the pressure tube 331 rises more than 2 in. of mercury above that in tube l5 and switch arm S03 is moved into engagement with contact Let it be assumed that wiper 388 remains in its previously adjusted position, and that switch Sill lis moved to its on position. Under these circumstances, the only circuits to windings 319 and 385 will include resistors 385 and .385, respectively. The circuit through winding 319 is from terminal 5l through Wire 52, resistor k335, winding 31,5, Wire 339, wire 55, and terminal .54. At the same time, current is flowing from ter- 5l .through wire 52, wire 353, resistor 386, vire winding 380, Wire 389, wire 55, and yterminal 5d. Thus, each of the resistors Yare in series with their respective windings and there is no voperation on ythe motor, arm 3GB remains at its eXtreme left position and cabin boost control H adds no signal to the turbo boost control system.

It now seen that when the aircraft is operated at high power outputs, the discharge pressure t 'is to remain higher than that necessary to mantain proper air flow into the cabin and the cabin boost control has no effect on the control oi the turbo-supercharger. If the airplane levels off for cruising at about 10,000 foot elevation, high power output may no longer be demanded and the turbo boost selector may be adjusted for a lower supercharger discharge pressure. Assume that wiper 22 'is adjusted to position 5 about midway across resistor 2l so that wire 3E) now becornes about l5 volts positive relative to wiper 22. If vcabin boost control l! be ignored, then the output signal of the turbo boost selector is equal to the 15 volts less than the 2 volts of the calibrating potentiometers, in other Words, 13 volts positive. The increase in positive signal from the turbo boost selector tends to cause an opening movement of the waste gate 3I6 and this in turn permits the supercharger discharge Vessure to drop. As the discharge pressure tops, wip-er of the induction pressure reve con roller moves to the right and, asg that there is neither excessive acceleration n overspeed, wipers 360 and tend to assume the positions shown on the drawing. Assuming that the discharge pressure drops to about 20 in. of mercury and that wiper 363 is about 2/3 oi the way across resistors 3(35, moving from the left, then it appears that wiper 353 is about 20 volts negative relative to 33B and the output from network 353 is 20 volts negative. With a positive 13 volt signal from the turbo boost selector, and a negative 20 volt signal from network 3i 3 due to drop in induction pressure, only a 7 volt positive signal is required from network 372 to balance the networks. Therefore, motor 3l8 is operated in a waste gate opening position due to the output of network 3 I 2 being, in its previous condition, more than 7 volts positive. This opening movement will continue until wiper 34M is only 7 volts positive relative to wiper 35i. The turbo boost control system thus tends to balance out to provide a turbo-supercharger discharge pres- -sure of about 20 inches of mercury, as previously noted. However, this is noted to be insuiicient for furnishing the desired airflow and it is obvious that the differential of pressure between tubes l5 and 337 has vanished. Thus, switch arm 3733 is moved into engagement with contact 333 by spring means 3M and resistor 386 in series with field winding 333 is shunted by a circuit from terminal 5l, wire 52, wire 338, switch 33i, wire 349, arm contact 355, wire 393, limit switch 383, wire 399, wire 397, winding 33E), wire 339, wire 55, and terminal lill. With resistor 38S shunted out and resistor 385 in its series relation with winding 379, motor 3M is operated to drive wiper 309 to the right across resistor 337. With a l5 volt potential existing between wiper 22 and wire 33, it is now noted that the same potential of 15 volts exists across resistor 337. At the extreme left position, wiper 339 is at the saine potential as wire 3i), but as it moves to the right, it becomes less positive relative to the ground and, at the extreme right is at ground potential. Assume that 339 is now at a position midway across resistor 337. In this position, wiper 3M! is now 'I1/2 volts negative relative to wire 3i). Wiper 333 is connected by wire 393 through wiper 388, wire 394, terminal 335i, wire 396, terminal 378, wire 377, to the right-hand eXtreme of resistor 374. It was previously noted that wiper 375 is 2 volts negative relative to the right-hand extreme of said resistor so wiper 375 is now at a potential of 51/2 volts positive relative to wiper 22 and the voltage signal from turbo boost selector becomes only 51/2 volts instead of the previous 13 volts. The reduction in positive signal from turbo boost selector l2 causes the negative signal of network 3i3 to cause motor 353 to operate in a direction to close waste gate 3l6. Closing waste gate 373 again raises the turbo-supercharger discharge pressure and causes the differential of pressure between tubes l5 and 337 to rise. Assuming that this diierential becomes 11/,3 in. of mercury. then arm 303 is moved midway between contacts 335 and 3% and neither resistor is shunted out of its circuit. With neither resistor shunted out, the currents supplied the windings oi motor 3537 are of like phase and the motor stops operating. Wiper 339 then remains at about its mid-position on resistor 387.

Had wiper 22 been adjusted to the extreme left of resistor 2i. and wire 3l) at a potential 30 volts above said wiper 22, then there would have been a 30 volt drop across resistor 337 and wiper in its mid-position on resistor 337 would be l5 volts negative relative to wire 3Q, or 13 volts posi- 'tive relative to wiper 22. Had wiper 22 been adjusted to a position 28 volts positive relative to the left of resistor 2l, so that normally there would be no signa1 of any sort from turbo boost selector i2, then there would be no voltage drop across resistor 387 and the position of wiper 333 would be of no effect.

lt is apparent that the ability of cabin boost control Il to modify the operation oi the turbosupercharger control system is dependent on the position oi wiper 22. This feature is of considerable importance for it provides a positive safeguard against increasing induction pressure to an unduly high value and thus endanger the engine. For instance, if the airplane were operating at a condition previously described wherein the induction pressure was about 2O inches of mercury, and cabin boost control il was compensating the control of the inboard engines to increase their induction pressure to about 23 inches of mercury, an emergency might arise which would require full engine power. To get full power, the pilot would fully open the throttles of engines 2 and 3, assuming that they were partly closed to keep their actual power output the saine as the outboard engines even though their induction pressures were above those of the outboard engines, and would adjust the turbo boost selector to its point of maximum power. While the added induction pressure and the increased differential pressure across tubes l5 and 337 would actuate arm. 3&3 to cause motor 367 to move wiper 399 to the left, this operation would take Some time, because of the relative slow motion of wiper 339 due to gear boX 3%8. In the meantime, if the voltage signal from turbo boost selector l2 was made less positive by action of cabin boost control il, the waste gate of the inboard engine or engines may be closed too far and result in damage to the turbo-supercharger or to the engine due to excessive pressures. However, with the present apparatus, as wiper 22 is moved to the right, and the positive signal is diminished, the voltage drop across resistor 387 and the compensating eiect of cabin boost control il is likewise diminished. The present cabin boost control is thus seen to be inherently safe.

In the above operation, it was assumed that the operation of the cabin boost control resulted in the induction pressure assuming such a value that the switch arm 3533 moved to a point inidway between contacts 335 and 306. Now let it be assumed that either because of a change in the setting of the turbo boost selector or for some other reason, the induction system pressure rises with respect to the cabin pressure so as to cause the switch blade 333 to move back into engagement with contact 335. Under previous conditions, limit switch 332 was open due to the slider 399 being in its extreme left hand position relative to resistor 337. In view of the fact, however, that the slider 3539 has been moved to an intermediate position, limit switch 332 is now closed with the result that a circuit is established to the motor held 'winding 379 independently of resistor 385 and shunting out resistor 385. This circuit is as follows: from terminal 5l through conductors 52 and 333, switch 33t, conductor 339, switch blade 363, contact 335, conductor 339, limit switch 382, conductor 357, motor field winding 372, and conductors 389 and 55 to terminal 5d. Under these conditions, the circuit to winding 379 does not include resistor 335 while the circuit to winding 380 includes resistor 385. Thus, the current through field winding 383 will now lead that through winding 379 with the result that the motor will be caused to rotate in such a direcr tion as to drive slider 309 to the left. This will 13 havev the opposite effect tothe movement of slider 309ftofthe right, previously considered. In other` Words,4 theA effect of thisY will be to bring the potential. of the right hand` terminal of resistor 314:'015 the Calibrating potentiometer more nearly that oi. conductor 30' so as to tend to lower the inductionpressure. This is desirable because with slider 39'in the position previously indicated, the inductionpressure is higher than necessary for eng-ine supercharging purposes. In this connection, it is to be borne in mind that if the increase in' induction system pressure was occasioned by amai/ement of slider 22 to the right, this decrease inthe eiiectof the cabin boost control would take place more or less automatically because of the decrease in the voltage across the resistor 381 of the cabin boost control potentiometer, as cxplained above. Thus, upon the raising of the setting of theV turbo boast control, there is an immediate decrease in the eiect of the cabin boost control: and as soon as the induction system pressurel starts to rise as a result o the movement; of' the turbo boost selector, the cabin boost control is immediately placed into operation to reduce` the induction system pressure to that just` necessary toY maintain the desired differenta'll..

The limit switches 382 and are provided for limiting the driving of the slider by the motor 301'.. Uponthe slider approaching either Xtreme position; the appropriate limit switch is opened. Each of these limit switches is in series with one of: th'ezshunt circuits so'thatv upon this limit switch being opened, that shunt circuit, the closure of which is causing rotation oi the motor, is opened.

if desired, a signal light Bte.- may be operated by a second throw on lirnit switch 3533 to indicate whenl wiper has moved to its extreme right of travel and thus indicates that no more coinn pensation can be added to the system automat"- ically. Further, wiper 383 may be adjusted across resistor 392' to diminish the eiect of movement of wiperllg across resistor 367 in decreasing the positivefsignal' from turbo boost selector ii. The righten'd' of. resistor ."i'is connected to wire andi therefore is at the same potential wire Sii, while the left end of resistor @S52 is conr wire 39.3' to wiper 359; When wiper left extreme, there is no potential drop across resistor 382w`nereas, if wiper 339 is at estreme 310B whereas, if it is intermediate the extremes '"5 ofresistor it assumes a potential value intermediate that eicisting between wire ed and wiper 3109". The relative eiect oi cabin boost control il in modifying the turbo boost control system may thus be manually adjusted by movement ci wiper 3`88across resistor 392. in the position wiper 38E shown, cabin boost control li has maximum authorityV in modifying the turbo boost control system, whereas, if wiper 38d is moved to its eX- treme right, cabin boost control l l' would have no oon'ipensat'ingr eiect.

Briey summarizing, it is noted that the present cabin boost control apparatus responds to the rate of airiiow into the aircraft cabin and automatically compensates an electronic turbosupercharger control system in such a manner as to' maintain the rate oi airflow between predetermined' limits. The authority ci the cabin boost control maybe manually' adjusted and further sfunder completeA dominance of the turbo boost selecto;` of the turbo-supercharger control system. Adjustment ci the turbo boostselector of the contro-l system to raise induction pressure automatically reduces any compensation being added to the system by the cabin boost control.

In studying the foregoing description and recital of operation or the present invention, many substitutions and equivalents become apparent to those skilled in art. Further, While certa-in values have been given and various apparatus rather specically described, it should be kept in mind that this has been done in the interest of properly describing the present apparatus and that the scope oi the present invention is to be determined only by the appended claims.

I claim as my 1'nventiorn l. In an electrical control network, a plurality oi individual circuits, common means for simultaneously adjusting all of said circuits, means for modifying the contr-ol oi one of said circuits, and means connecting said modifying means into said one circuit in such a manner that the auhority ci modifying means is dependent on adjustment of said common` means.

2. in a compound electrical network, a plurality of indi dual networks; an adjustable control network. common tc all of said individual networks for simultaneously adjusting same, means for modifying the adjustment oi one of said individual networks, and means connecting said modiiying rneans to said adjustable control network so that rate of modifica-tion permitted by said modifying means is dependent on the adjustment oi said control network.

3. In an aircraft having a plurality of devices to be controlled. individual control systems for each of said devices, means responsive to a condition indicative of a need for operation of a device for adjusting the control system of said device, means common to each 0i said systems for simultaneously adjusting all of said systems, and means connecting said condition responsive means said common means in such a manner that the rate of adjustment of said condition responsive means is dependent on the adjustment of common means.

fi. In a turbo-supercharger control system, a manually adjustable source oi electrical potential for adjusting said control system, means responsive to a condition indicative of the operation of said supercharger for varying said potential,l and circuit means connectingsaid responsive means into said control system in such a manner that the rate which said condition responsive means may vary said potential is dependent on the adjustment oi seid manually adjustable source.

5. In an aires it having a pressurized cabin, an engine having a turbo-supercharger for supplying air thereto, said supercharger also supplying air to said cabin, electrical apparatus including a ble impedance mea-ns for reguche'fae .'e l i bosupercharger, means responsive to the flow of air to said cabin, second impedance means adjusted by said now responsive means, and circuit means connecting inipdas and seid apparatus in such manner that an adjustment of either of said impedances may require an increase in turbosupercharger opera-tion but so that anincrease in operation caused by said second impedance is dependenton the adjustment of said manually adn justed impedance means.

6. In an electrical control network, a rst voltage divider including an impedance, a voltage supply and an output connection means; a second lil voltage divider including an impedance and having an output connection means, and means connecting the impedance of second voltage divider in series with the impedance the output connection means ci tls. named voltage divider.

7. In an electrical control circuit, a network having an input current supply and providing output signal potentials, said network including a v adjustable potentiometer means an auto: adjusted potentiometer, said manualiy adjusts Output values, said automatically adjusted potentiometer ble of varying the value said tentials an appreciable amount when said manually adjustable pc-tcntiomet is ac *or a v lue oi' potential but be ig capable of modilying the value ci the orL Aut a decreasing amount as the manual y ad. tab-le pctentioineter is adjusted for lower potential output signals.

8. In aircraf ,g a so; encicsure, a plurality of engines, a turbo-supercharger for each engine for supplying air thereto, at least one of said superchargers also supplying air to said enclosure, electric motor means for controlling each of said superchargers, electrical circuit means including -control devices for simultaneously controlling the operation of each of said motors and thus controlling the discharge pressures of said superchargers, said electrical circuit means controlling said motors in response to the voltage and phase relations of currents ilowingin said circuit means, means responsive to the iiow of to enclosure one supercharger, manual adjusting means for said circuit, and means actuated by said flow responsive means for adjusting the electrical circuit means in its control of the motor controlling said one supercharger, said actuated means vbeing arranged to cause adjustments of said circuit up to a relatively large amount when said manual adjustment means is adjusted to provide a low discharge pressure and to cause no more than a relatively small adjustment of said circuit when said manual means is adjusted to provide a high discharge pressure.

9. In an aircraft having a pressurized enclosure, a plurality of engines, a supercharger for each engine for supplying air thereto, reversible electric motor means for controlling each of said superchargers, electric circuit means including control devices for regulating the operation of said motors and thereby the operation of said superchargers, one of said control devices comprising a pressure selector means manually adjustable from low to high pressure settings for causing said superchargers to supply air under lower r higher pressures to said engines, at least one of said superchargers also supplying air to said enclosure, means responsive to the flow of air to said enclosure, and voltage modifying means adjusted by said flow responsive means, said voltage modifying means being connected in said circuit in a manner to modify the operation of said one supercharger, the permissible amount of such modiiication being diminished by adjusting said pressure selector means to higher settings.

if). In an aircraft having engines equipped with turbo-superchargers and having a pressurized cabin. at least one of said turbo-superchargers supplying air to its associated engine and to said cabin, control means for each of said turbosuperchargers, ,manual adjustment means for Cil simultaneously adjusting each of said control means, means responsive to the air ow from said one supercharger to said cabin, means adjusted by said flow responsive means for modifying said control means for said one supercharger in a manner to maintain said air iiow above a predetermined value, and means connecting said adjusted means into said control means in such manner that the modifying ability of said adjusted means is dependent on the manual adjustment of said control means.

Il. Control apparatus for an aircraft having an engine and a supercharger therefor and a pressurized cabin receiving air from said supercharger, said supercharger being normally controlled by an electrical system; comprising, combination, means responsive to a condition indicative of air i'iow to cabin. reversible power means controlled by said flow responsive means, impedance means adjusted by said power means, and means connecting said impedance means into the normal electrical control system of the supercharger.

12. In an electrical control system, a plurality of electrical networks, a voltage divider having an end connection and an intermediate connection, means impressing a potential across Said voltage divider, one of said networks being connected to said end connection, a second voltage divider having end connections and an interconnection, the end connections of said second voltage divider being connected in series with the end connection and intermediate connection of the nrst voltage divider, the intermediate connection of the second voltage divider being connected to another of said networks, the degree 0f control exercised by said second voltage divider being dependent on the adjustment of the intermediate connection of the first divider.

13. In an aircraft having a plurality of engines each equipped with a supercliarger, an individual device for controlling each of said superchargers, individual control systems for each of said devices, means responsive to a condition indicative of the operation of a supercharger for adjusting the control system for the device controlling said supercharger, means common to each 0f said systems for simultaneously adjusting all of said systems, and means connecting said condition responsive means to said common means in such a manner that the rate of adjustment of said condition responsive means is dependent on the adjustment of said common means.

lil. In an aircraft having an engine equipped with a turbo supercharger, a device for controlling said supercharger, a control system for said device, a manually adjustable source of electrical potential for said system, means responsive to a condition indicative of the operation of said supercharger for varying said potential, and circuit means for varying the rate at which said condition responsive means may vary said potential dependent on the adjustment of said manually adjustable source.

15. In an aircraft having a plurality of power means; a control device for each ci' said power means; and an electrical control system for said devices comprising, in combination, an individual lectrical network for each of said devices, a voltage divider having an end connection, means impressing a potential across said voltage divider, one of said networks being connected to said end connection, a second voltage divider having end connections and an intermediate connection, the end connections of said second voltagedivder being connected in series with the end connection and intermediate connection of the rst voltage divider, the intermediate connection of the second voltage divider being connected to another of said networks, the degree of control exercised by said second voltage divider being dependent on the adjustment of the intermediate connection of the rst divider.

DANIEL G. TAYLOR.

REFERENCES CITED Number 18 UNITED STATES PATENTS Name Date Stoller Oct. 17, 1933 Gregg May 21, 1935 Silverman May 5, 1936 Powell May 3, 1938 Price July 16, 1940 Roberts Oct. 22, 1940 Wagner Dec. 9, 1941 Nixon June 2, 1942 Bellows Apr, 6, 1943 Rogers Dec. 28, 1943 Jde June 6, 1944 Talbot July 11, 1944 

